Am I obligated to complete a discontinuous votive fast—fasting one day and breaking the fast the next—which I did not complete due to travel, or what should I do?

Undertaking a vow is disliked (makrooh). What you have undertaken is a conditional vow that must be fulfilled if the condition is met. If you did not intend consecutive fasting in your first and second vows, then complete what remains of them. But if you did intend them to be consecutive, then resume the fasting for both vows. And according to the majority of scholars, there is no expiation (kaffara) upon you.